Sourdough starter made with flour and water refreshed for 3 or more days

Sourdough (or, more formally, natural leaven or levain) refers to the process of leavening bread by capturing wild yeasts in a dough or batter, as opposed to using a domestic, purpose-cultured yeast such as Saccharomyces cerevisiae. Levain is a Bread Leavening agent used traditionally in France and today by artisan bakeries and hobbyists around the world A leavening agent (sometimes called just leavening or leaven) is a substance used in Doughs and batters that causes a foaming action intended Bread is a Staple food prepared by Baking a Dough of Flour and Water. Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described Saccharomyces cerevisiae is a Species of Budding Yeast. It is perhaps the most useful Yeast owing to its use since ancient times Sourdough more specifically refers to a symbiotic culture of lactobacilli and yeasts, giving a distinctively tangy or sour taste (hence its name), due mainly to the lactic acid and acetic acid produced by the lactobacilli. This article is about the biological phenomenon for other uses see Symbiosis (disambiguation The term symbiosis (from the Greek Lactobacillus is a Genus of Gram-positive Facultative anaerobic or Microaerophilic Bacteria. Yeasts are a growth form of eukaryotic Microorganisms classified in the kingdom Fungi, with about 1500 Species currently described Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role Acetic acid, also known as ethanoic acid, is an organic chemical compound, giving Vinegar its sour taste Though no longer the standard method for bread leavening in most developed countries (it was gradually replaced first by the use of barm from beermaking, then after the confirmation of germ theory by Louis Pasteur by cultured yeasts), some form of natural leaven is used in many specialty bakeries. Barm is the foam or scum formed on the top of liquor (ie fermented alcoholic beverages such as Beer or Wine, or feedstock for Hard liquor Beer is the world's oldest and most widely consumed Alcoholic beverage and the third most popular drink overall after water and tea The germ theory, also called the pathogenic theory of medicine, is a Theory that proposes that Microorganisms are the cause of many Diseases. Louis Pasteur (27 December 1822 – 28 September 1895 a French Chemist and Microbiologist, is best known for remarkable breakthroughs in the causes and

Sourdough bread is made by using a small amount (20-25%) of "starter" dough (sometimes known as "the mother sponge"), which contains the yeast culture, and mixing it with new flour and water. A pre-ferment (pâte fermentée also called a "sponge" or a "bread starter" is a Fermentation starter used in Bread Baking. Flour is a powder made of Cereal grains It is the key ingredient of Bread, which is a staple food in many countries and therefore the availability Part of this resulting dough is then saved to use as the starter for the next batch. As long as the starter dough is fed flour and water daily, the sourdough mixture can stay in room temperature indefinitely and remain healthy and usable. Dough is a paste made out of any Cereals (grains or leguminous crops by mixing the Flour with a small amount of Water. It is not uncommon for a baker's starter dough to have years of history, from many hundreds of previous batches. As a result each bakery's sourdough has a distinct taste. The combination of starter, yeast culture and air temperature, humidity, and elevation also makes each batch of sourdough different.

Biology and chemistry of sourdough

Two loaves of naturally-leavened (sourdough) bread.

A sourdough starter is a stable symbiotic culture of bacteria and yeast present in a mixture of flour and water. A pre-ferment (pâte fermentée also called a "sponge" or a "bread starter" is a Fermentation starter used in Bread Baking. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have Flour is a powder made of Cereal grains It is the key ingredient of Bread, which is a staple food in many countries and therefore the availability Water is a common Chemical substance that is essential for the survival of all known forms of Life. The yeasts Candida milleri or Saccharomyces exiguus usually populate sourdough cultures symbiotically with Lactobacillus sanfranciscensis. ^[1]. Lactobacillus sanfranciscensis (bacteria) was named for its discovery in San Francisco sourdough starters. Lactobacillus sanfranciscensis (formerly L sanfrancisco) is a species of Lactic acid bacteria that helps give Sourdough bread its

Often a starter will consist of basic items such as: water, bread flour, rye flour and a sourdough starter which can be purchased at certain grocery stores. Rye ( Secale cereale) is a grass grown extensively as a grain and forage crop Once the starter is made water and flour must be added in time increments over a period of days. Depending on the locale of the bakery and the type of bread being made, the starter can be either a relatively fluid batter or a stiffer dough; as a general rule, the more sour breads are made with a liquid starter. Firm starters (such as the Flemish Desem starter) are often more resource-intensive, traditionally being buried in a large container of flour to prevent drying out. Desem (Flemish for " Leaven " is a type of Sourdough starter made from whole wheat flour and water inoculated by wild yeasts and bacteria traditionally

A fresh culture begins with a mixture of flour and water. Fresh flour naturally contains a wide variety of yeast and bacteria spores. When wheat flour contacts water, naturally-occurring amylase enzymes break down the starch into complex sugars (sucrose and maltose); maltase converts the sugars into glucose and fructose that yeast can metabolize. Amylase is an Enzyme that breaks Starch down into Sugar. Amylase is present in human Saliva, where it begins the chemical process Solubility of Pure SucroseTemperature(Cg Maltose, or malt sugar is a Disaccharide formed from two units of Glucose joined with an α(1→4 linkage Maltase ( (acid maltase alpha-14-glucosidase is an Enzyme produced by the cells lining the Small intestine that breaks down the Disaccharide Maltose Glucose (Glc a Monosaccharide (or simple Sugar) also known as grape sugar, is an important Carbohydrate in Biology. Fructose (also levulose or laevulose) is a simple reducing Sugar ( Monosaccharide) found in many foods and is one of the three The lactobacteria feed mostly on the metabolism products from the yeast. ^[1] The mixture develops a balanced, symbiotic culture after repeated feedings.

There are several ways to increase the chances of creating a stable culture. Unbleached, unbromated flour contains more microorganisms than more processed flours. Flour bleaching agent is a Food additive added to Flour in order to make it appear whiter (freshly milled flour is yellowish and to oxidize the surfaces of the flour Potassium bromate (KBrO3 is a Bromate of Potassium and takes the form of white crystals or powder Bran-containing (wholemeal) flour provides the greatest variety of organisms and additional minerals, though some cultures use an initial mixture of white flour and rye flour or "seed" the culture using unwashed organic grapes (for the wild yeasts on their skins). Bran is the hard outer layer of Grain and consists of combined Aleurone and Pericarp. For the Tokyo University supercomputer see Gravity Pipe. GRAPE, or GRA phics P rogramming E nvironment is Using water from boiled potatoes also increases the leavening power of the bacteria, by providing additional starch. The potato is a Starchy Tuberous crop Vegetable from the perennial Solanum tuberosum of the Solanaceae Bakers recommend un-chlorinated water for feeding cultures. Adding a small quantity of diastatic malt provides maltase and simple sugars to support the yeasts initially. ^[2]

The flour-water mixture can also be inoculated from a previously kept culture. The culture is stable due to its ability to prevent colonization by other yeasts and bacteria as a result of its acidity and other anti-bacterial agents. The Bacteria ( singular: bacterium) are a large group of unicellular Microorganisms Typically a few Micrometres in length bacteria have In Computer science, ACID ( Atomicity Consistency Isolation Durability) is a set of properties that guarantee that Database transactions are As a result, many sourdough bread varieties tend to be relatively resistant to spoilage and mold.

The yeast and bacteria in the culture will cause a wheat-based dough, whose gluten has been developed sufficiently to retain gas, to leaven or rise. Wheat ( Triticum spp is a worldwide cultivated grass from the Levant area of the Middle East. Gluten is a composite of the proteins Gliadin and Glutenin. These exist conjoined with Starch, in the Endosperms of some Obtaining a satisfactory rise from sourdough, however, is more difficult than with packaged yeast, because the lactobacteria almost always outnumber the yeasts by a factor of between 100 and 1000, and the acidity of the bacteria inhibit the yeasts' gas production. The acidic conditions, along with the fact that the bacteria also produce enzymes which break down proteins, result in weaker gluten, and a denser finished product. ^[3]

Preparing sourdough products

Sourdough starter can be used in two different manners. Traditionally, a certain amount of sourdough starter (somewhere around 20-25% on average, depending on the water content of the starter) is mixed into the bread dough, and the bread is kneaded and allowed to rise as normal. The process is largely similar to using a pure strain of baker's yeast, although some care must be taken since the rise time of most sourdough starters is usually somewhat longer than the average for typical baker's yeasts. (As a result, many sourdough starters are unsuitable for use in a bread machine. ) When using a particularly liquid starter with a high concentration of lactobacillus or acetobacter organisms, the large amount of lactic and acetic acids produced needs to be managed carefully, since the acid can break down the gluten in the bread dough; this becomes less of a concern in a stiffer starter, where the yeast usually predominates.

The other manner of using sourdough starter is common for making quick breads or foods like pancakes. A quick bread is a type of Bread which is Leavened with chemical leaveners such as Baking powder, Sodium bicarbonate, or Cream of tartar Pancakes are a type of Flatbread prepared from a sweet batter that is cooked on a hot Griddle or in a Frying pan. It involves using baking soda (and sometimes baking powder) to neutralize some or all of the acid in the starter, with the acid-base reaction generating carbon dioxide to provide lift to the dough or batter in a manner very similar to Irish soda bread. Sodium bicarbonate or sodium hydrogen carbonate is the Chemical compound with the formula NaHCO3 Baking powder is a dry chemical Leavening agent used in cooking mainly baking Carbon dioxide ( Chemical formula:) is a Chemical compound composed of two Oxygen Atoms covalently bonded to a single Soda bread is a type of Quick bread in which Baking soda has been substituted for yeast This technique is particularly common in kitchens where the starter is intentionally kept off-balance, with a substantially high acid level, and is particularly associated with areas such as Alaska.

History of sourdough

Sourdough bread

Sourdough likely originated in Ancient Egyptian times around 1500 BC, and was likely the first form of leavening available to bakers. Ancient Egyptian cuisine covers a span of over three thousand years but still retained many consistent traits until well into Greco-Roman times Sourdough remained the usual form of leavening down into the European Middle Ages^[4] until being replaced by barm from the beer brewing process, and then later purpose-cultured yeast. Barm is the foam or scum formed on the top of liquor (ie fermented alcoholic beverages such as Beer or Wine, or feedstock for Hard liquor

Bread made from 100% rye flour, which is very popular in the northern half of Europe, is usually leavened with sourdough. Rye ( Secale cereale) is a grass grown extensively as a grain and forage crop Baker's yeast is not useful as a leavening agent for rye bread, as rye does not contain enough gluten. A leavening agent (sometimes called just leavening or leaven) is a substance used in Doughs and batters that causes a foaming action intended Gluten is a composite of the proteins Gliadin and Glutenin. These exist conjoined with Starch, in the Endosperms of some The structure of rye bread is based primarily on the starch in the flour, as well as other carbohydrates known as pentosans; however, rye amylase is active at substantially higher temperatures than wheat amylase, causing the structure of the bread to disintegrate as the starches are broken down during cooking. Starch, CAS # 9005-25-8 Chemical formula (C6H10O5n is a Polysaccharide Amylase is an Enzyme that breaks Starch down into Sugar. Amylase is present in human Saliva, where it begins the chemical process The lowered pH of a sourdough starter therefore inactivates the amylases when heat cannot, allowing the carbohydrates in the bread to gel and set properly. pH is the measure of the acidity or alkalinity of a Solution. ^[5] In the southern part of Europe, where baguette and even panettone were originally made with wheat flour and rye flour has become less common as the standard of living has risen, it has been replaced by the faster growing baker's yeast, sometimes supplemented with longer fermentation rests to allow for some bacterial activity to build flavor. A baguette (bəˈɡɛt is a variety of Bread distinguishable by its length very crispy crust and slits cut into it to enable proper expansion Panettone ( Milanese: panetton classical orthography panetùn other orthography is a typical Bread of Milan

Sourdough was the main bread made in Northern California during the California Gold Rush, and it remains a part of the culture of San Francisco today. Northern California is the northern portion of the US state of California. The California Gold Rush (1848&ndash1855 began on January 24 1848 when Gold was discovered by James Marshall at Sutter's Mill in Coloma, California The City and County of San Francisco is the fourth most populous city The bread became so common that "sourdough" became a general nickname for the gold prospectors. The nickname remains in "Sourdough Sam", the mascot of the San Francisco 49ers. Sourdough Sam is a mascot for the NFL 's San Francisco 49ers. The term mascot – defined as a term for any person animal or object thought to bring Luck – colloquially includes anything used to represent a group with a common The San Francisco 49ers are a professional American football team

The sourdough tradition was carried into Alaska and the western Canadian territories during the Klondike Gold Rush. The Klondike Gold Rush, infrequently referred to as the Yukon Gold Rush or Alaska Gold Rush, was a frenzy of Gold rush Immigration to and for Conventional leavenings such as yeast and baking soda were much less reliable in the conditions faced by the prospectors. The sourdough starter, however, had to be kept warm to survive. Experienced miners and other settlers frequently carried a pouch of starter either around their neck or on a belt and were often fiercely guarded. Old hands came to be called "sourdoughs", a term that is still applied to any Alaskan old-timer. [2]

San Francisco sourdough is the most famous sourdough bread made in the US. In contrast to the majority of the country, it has remained in continuous production for nearly 150 years, with some bakeries able to trace their starters back to California's territorial period. It is a white bread, characterized by a pronounced sourness (not all varieties are as sour as the San Francisco sourdough), so much so that the dominant strain of lactobacillus in sourdough starters was named Lactobacillus sanfranciscensis. Sourdough also became popular because of its ability to combine well with seafoods and soups such as cioppino, clam chowder and chili. Cioppino is a Fish Stew derived from the various regional fish Soups and stews of Italian cuisine.

Sourdough has not enjoyed the popularity it once had since bread became mass-produced. Manufacturers make up for the lack of yeast and bacteria culture by introducing an artificially-made mix known as bread improver into their dough. Bread improver has been a common ingredient in Bread since the early 1950s and is used to speed up bread production

Sourdough breads

Aside from what might be called plain sourdough bread, there are a number of other breads that use similar starters and techniques. Amish Friendship Bread uses a sourdough starter that includes sugar and milk. Amish Friendship Bread is a type of Sourdough starter that is often shared in a manner similar to a Chain letter. Sugar is a class of edible Crystalline substances mainly Sucrose, Lactose, and Fructose. Milk is an opaque white liquid produced by the Mammary glands of female Mammals (including Monotremes. However, it is further leavened with baking powder and baking soda, making it more of a quick bread. Baking powder is a dry chemical Leavening agent used in cooking mainly baking Sodium bicarbonate or sodium hydrogen carbonate is the Chemical compound with the formula NaHCO3 A quick bread is a type of Bread which is Leavened with chemical leaveners such as Baking powder, Sodium bicarbonate, or Cream of tartar The German Pumpernickel, is traditionally made from a sourdough starter, although modern pumpernickel loaves often use commercial yeasts, sometimes spiked with citric acid or lactic acid to inactivate the amylases in the rye flour. Pumpernickel is a type of German Bread traditionally made with coarsely-ground rye meal Citric acid is a weak organic Acid. It is a natural Preservative and is also used to add an acidic or sour taste to foods and Soft drinks Lactic acid ( IUPAC Systematic name: 2-hydroxypropanoic acid) also known as milk acid, is a Chemical compound that plays a role Amylase is an Enzyme that breaks Starch down into Sugar. Amylase is present in human Saliva, where it begins the chemical process Also, the Flemish Desem bread is a popular form of whole-wheat sourdough, though cultured in a much less liquid medium. Desem (Flemish for " Leaven " is a type of Sourdough starter made from whole wheat flour and water inoculated by wild yeasts and bacteria traditionally

Other recipes use starters that aren't actually truly natural leavens. The Italian Biga and French Poolish add sourdough-like flavors to breads by allowing the yeast a lengthy half-day or longer fermentation. Biga is a type of Pre-ferment used in Italian Baking. Many popular Italian Breads including Ciabatta, are made using a A pre-ferment (pâte fermentée also called a "sponge" or a "bread starter" is a Fermentation starter used in Bread Baking. Unlike a true sourdough, these recipes usually start with commercial yeast, and cultivation of lactobacillus bacteria is generally an incidental effect.

See also

• Salt rising bread
• Klondike Gold Rush where sourdough was a word for a miner in his first year

External links

• Usenet rec.food.sourdough FAQ, including further HOWTOs and links to suppliers and recipes
• Sourdough Companion - A Sourdough Bread Community, videos and tutorials
• Modeling of Growth of Lactobacillus sanfranciscensis and Candida milleri... from Applied and Environmental Microbiology, July 1998, by Gänzle et al. Salt rising (or salt risen bread is bread in which the bacterium Clostridium perfringens is used to leaven the bread rather than Yeast or Baking soda. The Klondike Gold Rush, infrequently referred to as the Yukon Gold Rush or Alaska Gold Rush, was a frenzy of Gold rush Immigration to and for , Universität Hohenheim
• [3] Recipe, discussion and pictures of making sourdough bread.
• SourDom's Beginners' Blog - A series of 5 basic tutorials on sourdough baking
• The Yeast Beacon - A tutorial on growing your own sourdough
• 1847 Oregon Trail Sourdough Starter - A source for free sourdough starter.

References

1. ^ Rosada, Didier (1997) Advanced Sourdough. Minneapolis: National Baking Center.
2. ^ Reinhart, Peter (1998) Crust & Crumb: Master formulas for serious bread bakers. Berkeley: Ten Speed Press. ISBN 1-58008-003-0
3. ^ McGee, Harold (2004). On Food and Cooking: The Science and Lore of the Kitchen, 544. New York: Scribner. ISBN 0-684-80001-2
4. ^ Hieatt, Constance et al. , Pleyn Delit, 2ed, Toronto: University of Toronto Press, 1996, ISBN 0802076327.
5. ^ Wing, Daniel, and Alan Scott. The Bread Builders, White River Junction (VT), Chelsea Green Publishing, 1999.